Solar Pro 4 (Reasoning)
by Upstage
Solar Pro 4 (Reasoning) is a reasoning model from Upstage, released on August 6, 2026. It has a 524K-token context window and can generate up to 131K output tokens. API pricing is $0.3 per 1M input tokens and $1.2 per 1M output tokens. It ranks #64 of 220 models by Intelligence Score with a score of 35.
Solar Pro 4 is Upstage's proprietary reasoning-focused agentic LLM (text→text) for finishing multi-step commercial work: long documents, terminal tasks, and multi-turn tool use. Supports English, Korean, and Japanese with a ~512K context window (OpenRouter listing ~524K) and up to 128K output tokens. Reasoning effort is adjustable (high for deep analysis, low for fast chat). Vendor/AA self-reported highlights include Terminal-Bench v2.1 57, τ³-Banking 23, AA-LCR 71, and GPQA Diamond 89.0; in-house asterisk rows include BrowseComp 49.2, SWE-Bench Verified (OpenHands) 70.6, MMLU-Pro 86.3, LiveCodeBench 87.8, AIME 2026 95.3. GDPval-AA v2 38.8 is noted here only — catalog gdpval-aa is Elo-scale (max_score 3000) and 38.8 does not fit that encoding (no gdpval-aa-v2 id). Standard list pricing is $0.30 input / $0.06 cached input / $1.20 output per 1M tokens; launch promo is 90% off on Upstage Console and OpenRouter through September 10, 2026 (23:59 UTC) — promo not stored in the provider price row. Also available via SolarChat, Hermes Agent, and Upstage Studio.
Key specs
| Provider | Upstage |
|---|---|
| Release date | 2026-08-06 |
| License | proprietary |
| Context window | 524K tokens |
| Max output | 131K tokens |
| Input price | $0.3 / 1M tokens |
| Output price | $1.2 / 1M tokens |
| Intelligence Score | 35 |
| Coding index | 20.8 |
Quick answers
What is the context window of Solar Pro 4 (Reasoning)?
Solar Pro 4 (Reasoning) has a context window of 524K tokens, with a maximum output of 131K tokens per response.
How much does Solar Pro 4 (Reasoning) cost?
Solar Pro 4 (Reasoning) costs $0.3 per 1M input tokens and $1.2 per 1M output tokens through the API.
Is Solar Pro 4 (Reasoning) open source?
No. Solar Pro 4 (Reasoning) is a proprietary model from Upstage (proprietary license).
When was Solar Pro 4 (Reasoning) released?
Upstage released Solar Pro 4 (Reasoning) on August 6, 2026.
How does Solar Pro 4 (Reasoning) compare to Claude Opus 5.5 (Reasoning)?
Solar Pro 4 (Reasoning) scores 35 on the Intelligence Score versus 60.5 for Claude Opus 5.5 (Reasoning), the current #1. Input pricing is $0.3 vs $4 per 1M tokens.
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